Secretary for Food and Health Dr Ko Wing-man on Thursday rejected calls for widening a ban on mainland live poultry imports amid growing threats of the H7N9 bird flu virus.

Ko said the current suspension on live poultry from Shenzhen had been “more than adequate” and hinted that it would be overacting to extend the ban to other parts of the mainland at present.

“Although [mainland authorities] have detected the H7N9 virus in samples taken in two [Shenzhen] markets, there has not been evidence so far they are the sources of the two human cases of Hong Kong,” he said.

“So, I gather that it is suitable to maintain the status quo,” he said. “Our measure [of banning imports from Shenzhen] has already gone beyond what is generally required,” he said.

But Ko said the government would keep an eye on the development and would reassess the measures when new situations arose.

The bird flu scare in Hong Kong has deepened after samples from two Shenzhen wet markets have tested positive for the H7N9 virus that has infected two Hong Kong residents who recently visited Shenzhen.

The Health and Family Planning Commission of Guangdong said on Wednesday that H7N9 had been detected in three samples taken from poultry stalls at two wet markets in the Longgang district in Shenzhen.

The infected samples were among 70 collected from 13 wet markets across Shenzhen. One sample came from a chopping board at a stall while the other two were found in chicken excrement and a plucking machine.

Shenzhen authorities have ordered the closure of chicken stalls in the two wet markets in question for Thursday for a thorough clean-up.

University of Hong Kong microbiologist Dr Ho Pak-leung said he believed the deadly virus was already spreading in Guangdong and the surrounding areas. He urged the Hong Kong government to stop live poultry imports from the mainland.

His fellow colleague in the university, Professor Yuen Kwok-yung, however, said a ban on all live chickens from the mainland was unnecessary.

So far, there are two confirmed human cases in Hong Kong.

An Indonesian maid, 36, fell sick on her return from Shenzhen and was later found to have contracted H7N9 bird flu after handling a live chicken at a flat near one of the infected wet markets in Shenzhen.

The second Hong Kong patient is an 80-year-old man who lives in Shenzhen. He had not handled live chickens.